Myanmar (BBN)-Nearly 50 soldiers have been killed in three days of fighting between government troops and Kokang ethnic rebels in Myanmar, state media report.
The Global New Light of Myanmar newspaper said airstrikes had been used in the response to the flare-up in Shan state, near the Chinese border, reports BBC.
The BBC's Myanmar correspondent, Jonah Fisher, says it is the heaviest fighting in at least two years.
It comes as the government tries to sign a peace deal with rebel groups.
The newspaper said there had been at least 13 separate clashes in the area in recent days with the Kokang rebels, known as the Myanmar National Democratic Alliance Army (MNDAA).
At least 47 soldiers were killed and more than 70 injured, it said. It did not indicate any rebel casualty figures.
There are reports that thousands of people have fled, including some who have crossed the border in to China.
Myanmar (also known as Burma) said it had formally informed China of the fighting.
Myanmar has been trying for decades to contain conflicts involving ethnic rebel movements seeking greater autonomy.
President Thein Sein has been pushing for peace deals with these groups, and while many have come into the political fold sporadic outbreaks of violence have continued.
The MNDAA were once a major part of the Burmese Communist Party guerrilla movement, which signed a peace deal with the military government in 1989.
But the deal broke down in 2009, when the government began pressuring rebel armies to join a national border guard force under central leadership.
BBN/SS-13Feb15-11:00am (BST)